Green’s Dictionary of Slang

(US) a passenger on a day-trip excursion, also attrib.

1983		Philadelphia inquirer (PA) 7 Aug. 2-J/2: Anyone who grew up at the beach will cheer Aaron Lucier’s ‘Shoobie-Eating Monster’: Shoobies [...] are tourists.
1985		E. Leonard Glitz 111: You had your shoobies, people’d bring their lunch in a shoebox, eat on the Broadwalk or out on the beach.
1993		Courier-Post (Camden, NJ) 25 June 65/1: Matthew [...] is chaning his wet bathing suit in the back seat of the family car [...] — in traditional shoobie fashion.
1998		Asbury Park Press (NJ) 25 May 72/1: That distinctively South Jersey ex[pression ‘shoobie,’ meaning a person who visits the sea shore for a single day.
2008		Philadelphia Inquirer (PA) 4 July W18/4: Folks go to Nantasket Beach for a day. Bu they don’t use the term ‘shoobie’.
2017		Philadelphia Dly News (PA) 21 May 25/2: Things shoobies do that annoy locals [...] Boot camp on the beach [etc].